The objective of this project is to develop and study methods of protecting the function of the heart during and after open-heart surgery. Although the patient is protected to a substantial degree by the cardiopulmonary bypass apparatus during cardiac surgery, it is often necessary to interrupt blood flow to the heart itself during open-heart surgery. We are attempting to define methods to protect the integrity of the heart during these periods of blood deprivation. Using cardiac function studies, metabolic determinations (intramyocardial oxygen and carbon dioxide tissue gas tensions) and pathological observations, we are studying the effects of interrupted nutrient cardiac blood flow and are using cardiac cooling, drugs, and varying ionic solutions and concentrations to minimize the degree of cardiac injury. We are also looking at the effects of converting the linear blood flow of the standard cardiopulmonary bypass pump to a more physiological pulsatile contour and assessing the effects of this change on cardiac and other body organ functions after surgery. We are also monitoring intramyocardial gas tensions in patients undergoing heart valve replacement in an attempt to identify those patients who need additional support for their heart function after the heart surgery itself.